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Research Papers

Influence of Circumferential Inflow Distortion on the Performance of a Low Speed, High Aspect Ratio Contra Rotating Axial Fan

[+] Author and Article Information
Chetan Mistry

e-mail: csmistry@rediffmail.com

A. M. Pradeep

e-mail: ampradeep@aero.iitb.ac.in
Department of Aerospace Engineering,
Indian Institute of Technology Bombay,
Powai, Mumbai 400076, India

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 26, 2013; final manuscript received October 15, 2013; published online January 2, 2014. Assoc. Editor: Aspi Wadia.

J. Turbomach 136(7), 071009 (Jan 02, 2014) (11 pages) Paper No: TURBO-13-1200; doi: 10.1115/1.4025953 History: Received August 26, 2013; Revised October 15, 2013

The influence of circumferential inflow distorted on the performance and flow behavior of a high aspect ratio, low speed contra rotating fan is reported in this paper. The total pressure at the inlet is artificially distorted by means of 90 deg mesh sector with a porosity of 0.70. The performance of the contra rotating fan was studied under different speed combinations of the two rotors under clean and distorted inflow conditions. Detailed flow analyses were conducted under design and off-design conditions. In order to understand the effect of distortion and its extent, the distortion sector was rotated circumferentially at intervals of 15 deg to cover the entire annulus. Detailed measurements of the total pressure, velocity components, and flow angles were carried out at the inlet of the first rotor, between the two rotors, and at the exit of the second rotor. The study reveals a few interesting aspects on the effect of inflow distortion on the performance of a contra-rotating stage. For the design speed combination and lower rotational speed of rotor-2, a reduction in the overall operating range with a shift of the peak pressure point towards higher mass flow rate, was observed. It is observed that the effect of inflow distortion at the inlet of rotor-1 gets transferred in the direction of rotor-1 rotation and spreads across the entire annulus. The opposite sense of rotation of rotor-2 causes the distortion effect to get transferred in the direction of rotation of rotor-2 with an associated reduction in the total pressure near the hub. It is observed that a higher rotational speed of the second rotor has a beneficial effect on the overall performance due to the strong suction by generated higher rotational speed of rotor-2.

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Figures

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Fig. 1

Schematic of the experimental setup

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Fig. 2

(a) Probe locations for clean inflow and (b) probe locations for distorted inflow

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Fig. 3

Probe locations for distorted inflow

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Fig. 4

Performance characteristic curves under different inflow conditions

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Fig. 5

Variation in the overall efficiency under clean and distorted inflow conditions

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Fig. 6

Variation of performance of rotor-1 under different inflow conditions

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Fig. 7

Variation of performance of rotor-2 under different inflow conditions

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Fig. 8

Variation of performance of rotor-1 under distortion facing condition

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Fig. 9

Variation of performance of rotor-2 under distortion facing condition

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Fig. 10

Total pressure coefficient at inlet, exit of rotor-1, and rotor-2 at Nd-Nd speed combination

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Fig. 11

Total pressure coefficient at inlet, exit of rotor-1, and rotor-2 at Nd-0.91 Nd speed combination

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Fig. 12

Total pressure coefficient at inlet, exit of rotor-1, and rotor-2 at Nd-1.08 Nd speed combination

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Fig. 13

Static pressure coefficient at the inlet of rotor-1, exit of rotor-1, and rotor-2 at Nd-Nd speed combination

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Fig. 14

Circumferential variation of spanwise total pressure rise coefficient (a) design mass flow rate (b) peak pressure mass flow rate

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Fig. 15

Radial distribution of absolute flow angle at the (a) exit of rotor-1 and (b) exit of rotor-2 for design mass flow

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Fig. 16

Radial distribution of absolute flow angle at the (a) exit of rotor-1 and (b) exit of rotor-2 for peak pressure mass flow

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Fig. 17

Flow angle variation along the stage with upstream flow redistribution

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